Process for obtaining deproteinized tobacco freed of nicotine and green pigment, for use as a smoking product

ABSTRACT

Described herein is a process for obtaining a smoking product from tobacco leaves. The leaves, or leaves and stalk together when immature plants are used in the process, are ground or otherwise pulverized to liberate the liquid portion of the leaves from the plant material. The liquid portion of the leaves is treated to remove water-soluble proteins and nicotine and the solid portion of the leaves is treated to remove water and insoluble protein material, nicotine and green pigment material. The residues obtained after separation of the water-soluble and -insoluble protein, nicotine and green pigment material are recombined to yield a processed tobacco which is suitable for use in cigarettes as a tobacco filler or other products of tobacco manufacture.

FIELD OF THE INVENTION

In a broad aspect, this invention relates to a process for obtaining asmoking product from tobacco plants. In another and more specificaspect, it relates to a process for removing protein, nicotine and greenpigment materials from tobacco which is to be used in cigarettes orother products of tobacco manufacture.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and incorporates by reference, as thoughfully set forth herein, the disclosure of the co-pending and commonlyassigned application of S. G. Wildman and P. Kwanyuen, entitled "Processfor Isolation of Proteins From Plant Leaves," filed Sept. 24, 1979,having Ser. No. 78,505.

BACKGROUND

Cigarettes and other products of tobacco manufacture are, for the mostpart, blends of two principal types of tobacco, so-called "flue-cured"and "burley" tobaccos. American cigarettes, for example, are generallycomprised of two-thirds flue-cured tobacco and one-third burley tobacco.

For the most part, the cultivation of flue-cured and burley tobaccosoccurs in the states of North Carolina, Virginia, Kentucky, Tennessee,South Carolina and Georgia. Production of flue-cured tobacco is largelyin a region adjacent to the Atlantic Coast whereas burley tobacco isgrown in more inland and upland regions. The growing and harvesting offlue-cured tobacco and burley tobacco differ in a number of respects.

In the case of flue-cured tobacco, the lowermost leaves are detachedfrom the plant stalk as they mature and begin to yellow. The detachedleaves are suspended in bunches on sticks which are hung in barns andthe tobacco "flue-cured," i.e., dried by air heated by heat exchangewith hot air passing through flues.

Burley tobacco, on the other hand, is allowed to mature until nearly allof the leaves on the stalks have yellowed. Then the entire plant is cutoff near the ground and the stalk and leaves allowed to wilt in thefield over a period of several days. The entire plant is then hung inspecially designed barns where it is allowed to air-dry in a slow curingprocess.

The cultivation of tobacco, particularly flue-cured tobacco, is alabor-intensive process. Therefore, there has been the inevitable trendtowards mechanization of this process. To that end, the United StatesDepartment of Agriculture has developed a process known as the"homogenized leaf-curing process," which is less expensive than theconventional curing processes.

In this process, the yellowed leaves of tobacco plants grown in theconventional manner are harvested and pulped. Water is added to the pulpwhich is then agitated at a temperature of about 25° C. for about 24hours. During this time, the proteolytic enzymes already in the leavesdigest some of the proteins that remain in the leaves at the time theyare harvested. After the digestion, the excess water is squeezed out ofthe now dark-brown pulp, which is then dried and serves as a startingmaterial for a reconstituted tobacco product used as a tobacco filler incigarette manufacture much like the low-quality tobacco obtained as aproduct of conventional curing processes.

The resulting product is somewhat safer for smoking than tobaccoobtained from conventional curing processes since it has a diminishedprotein concentration, proteins being one source of the undesirableproducts in cigarette smoke.

As in conventional cultivation, it is of the utmost importance that thetobacco leaves be allowed to turn yellow in the natural way before theyare harvested for use in the homogenized leaf-curing process.Nevertheless, the homogenized curing process is not capable of removingsufficient green pigment material from the leaves to the extent that theproduct has been acceptable to the tobacco industry.

In the course of the slow-burning characteristic of tobacco productssuch as cigarettes, pipe tobacco and cigars, nicotine, "tars," and otherproducts considered to have adverse effects on the smoker's health areliberated in the smoke which is drawn into the smoker's mouth and lungs.In view of health considerations, cigarette manufacturers have devisedsystems to reduce the nicotine and tar content of the burning tobacco.However, the biggest part of this reduction has not been achieved bydeveloping new kinds of tobacco low in tar and nicotine. Instead, it hasbeen achieved by changing the manner in which the cigarette isconstructed.

Thus, filters that reduce some of the tar content have become widelyused. However, most of the reduction has come from so-called "bypass"systems which utilize porous paper in the manufacture of cigaretteswhich permit air to be drawn through pores in the paper to dilute thegases generated by burning tobacco.

Although these techniques have resulted in a safer smoking product, theydo not remove all of the undesirable constituents in the tobacco smoke.Furthermore, these processes result in a reduction in the flavorcomponents of the smoke and this reduction in taste has been criticizedby smokers. Accordingly, there exists a need for the development of atobacco product which is inherently low in nicotine and tars but thatretains important flavor ingredients.

Accordingly, an object of the present invention is a tobacco productsuitable for use in cigarettes and other tobacco manufactures which hasa reduced protein, nicotine and tar content but which retains desirableflavor constituents.

Another object of this invention is to make available a process forobtaining a tobacco product suitable for use in cigarettes and othersmoking products which is less labor-intensive than conventionalprocesses.

That these and other objects may be accomplished by the presentinvention will be apparent to those skilled in the art from thefollowing summary and detailed description of the invention.

SUMMARY OF THE INVENTION

The present invention provides a process for treating tobacco, evenimmature tobacco, to obtain a deproteinized tobacco material suited foruse in cigarettes and other tobacco products having a reduced tarcontent and from which nicotine and green pigments have been removed.The process comprises converting tobacco to a pulp comprising a liquidportion and a solids portion, the latter comprising coarse fibrousmaterial and finely particulate material. The liquid portion, a solutionof water-soluble protein and other water-soluble plant material, isdeproteinized and treated to remove nicotine.

The pigments are removed from the coarse fibrous material and the finelyparticulate material and separated into green pigments and non-greenpigments. The non-green pigments, deproteinized solution and depigmentedfibrous material are combined to obtain a tobacco product suitable foruse as filler tobacco in cigarettes and other tobacco manufactures.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention can be used to obtain adeproteinized tobacco product which is freed of nicotine and greenpigment materials from the leaves of tobacco plants of all types. Theprocess is well-suited to the large-scale processing of eitherflue-cured or burley-type tobaccos, the tobaccos most widely used incigarette manufacture.

The process of the present invention can utilize the leaves of maturetobacco plants as used in conventional processes. However, it is alsosuited for the use of the leaves of plants which are short of maturity,i.e., leaves which have not yet begun to yellow naturally. In the lattercase, and particularly if the plants are quite immature, the entireplant, i.e., leaves and stalk, are utilized in the invention.

The ability of the process of the present invention to be applied toimmature plants has the advantage that only a relatively short growingperiod is required before the plants are harvested for use in theprocess. In areas where the growing season is sufficiently long, thiswill permit more than one crop to be grown in a single growing season.

After detachment of the leaves from the tobacco plant, the leaves, orleaves and stalk together if small plants are the source of the leaves,are ground, crushed, or otherwise reduced to a pulp to release theliquid portion of the leaves from the solids. This liquid portioncontains the water-soluble proteins occurring in tobacco. The liquidportion is preferably deproteinized in accordance with the processdescribed in the co-pending application for United States patent ofWildman and Kwanyuen, identified above.

Use of that process permits the isolation of ribulose 1,5-diphosphatecarboxylase, known to those in the art as "Fraction I" protein, acommercially valuable product, and Fraction II protein. In that process,after detachment of the leaves from the tobacco plant, the leaves, orleaves and stalk together if small plants are the source of the leaves,are ground, crushed or otherwise reduced to a pulp to release the liquidportion of the leaves from the solids. Preferably, the pulping processis carried out in the presence of a reducing agent. In that regard, thepulping process permits phenol oxidase enzymes present in the leaves tocontact the leaf proteins. This results in oxidation of aromatic aminoacids such as tyrosine which comprise part of the primary structure ofproteins. This oxidation modifies the protein, made visually manifest bytheir becoming brown, and lowers their solubility in water. The reducingagent, in effect, acts as an antioxidant to suppress this oxidation.

The presently preferred reducing agent for use in the invention is2-mercaptoethanol because it is volatile and evaporates during thefurther processing described below, leaving little or no residue in thematerial isolated. However, other reducing agents may also be used.Among these are agents such as sodium metabisulfite and dithiothreitol.

Separation of the residue of these agents, if any, can be done usingconventional techniques. The amount of reducing agent sufficient tocontrol the oxidation can vary depending, for example, on the agentselected. In the case of 2-mercaptoethanol, effective suppression of theundesirable oxidation can be achieved using about 5 milliliters of theliquid agent per kilogram of plant material being processed.

The liquid portion of the plant material contains the plant proteins indissolved form. Heat treatment of the liquid portion of the pulpcontaining the ribulose 1,5-diphosphate carboxylase followed by coolinginduces this protein to crystallize from the liquid. The mechanism bywhich the heat treatment induces crystallization is not clear. However,it is believed that the heat treatment modifies the protein in some waythat favors crystallization.

The solid matter in the pulp induces green-pigmented coarse, easilyseparated material and finely particulate green-pigmented material whichis difficult to separate from the liquid and which comprises pigmentmaterials, starch material and water-insoluble protein material.However, the heat treatment of this invention, the details of which willbe described below, in addition to inducing crystallization of theFraction I protein also causes partial coagulation of the finelyparticulate green-pigmented material which facilitates its removalduring further processing. For example, this material can be removed bymoderate centrifugal force. Therefore, the heat treatment is applied tothe liquid portion prior to separation of the liquid portion from thecoarse solid material. Heating of the entire pulp, i.e., prior toremoval of any solid material, is preferred because better yields to thecrystalline ribulose 1,5-diphosphate carboxylase are obtained in thisway than if heating is performed after removal of the coarse materialbut prior to removal of the pigmented material.

The heating step is carried out at a temperature and for a timesufficient to induce crystallization of ribulose 1,5-diphosphatecarboxylase, as octagonal crystals, from the liquid portion of the pulpwhen the liquid is cooled. However, in no instance should the liquidportion be heated in excess of the temperature at which the proteindenatures, about 52° C., and precipitates immediately as an insolublemass.

Although lower temperatures than 52° C. may be used, it is preferred touse a temperature of at least about 48° C., as below that temperaturethe green-pigmented materials do not coagulate sufficiently to permittheir easy removal. Furthermore, below 48° C. the heating time requiredto induce the crystallization of ribulose 1,5-diphosphate carboxylasemay be inconveniently long. Best results are obtained by heating theliquid portion to 50°±1° C. for from about 15 to 20 minutes.

The passage of time between harvesting the leaves, converting them to apulp and heating the pulp as described above reduces the yield of thecrystalline ribulose 1,5-diphosphate carboxylase which can be achievedby the process of the present invention. Therefore, these steps shouldbe delayed for as short a time as possible. To that end, it is preferredto perform these operations at or near the site of cultivation as theleaves are harvested.

Conversion of the leaves to a pulp can be by grinding, crushing or anyother suitable process.

The heat treatment can be performed either as a continuous or batchprocess. In a batch process, the pulp is placed in a vessel whereby heatis transferred to the pulp under conditions where no part of the pulp,or at least the liquid portion thereof, is heated to a temperature atwhich the protein denatures. As indicated above, preferably the pulp isheated to a temperature of 50°±1° C. for from about 15 minutes to about20 minutes.

In a continuous process, the pulp is pumped without undue agitationthrough coils immersed in a liquid heated to a temperature such that, byheat exchange, a specified volume of pulp would be heated to 50°±1° C.for from about 15 minutes to about 20 minutes and then through coils incontact with liquid at a temperature lower than 50° C. to reduce thetemperature of the pulp.

After having been heated, the liquid and solid portions of the pulp areseparated. Separation is conveniently accomplished by first pressing thepulp to express the liquid portion therefrom. The liquid obtained inthis way is a "green juice" containing the green-pigmented material.When heated above about 48° C. to cause its coagulation, this materialis simply removed, for example, by filtration or moderatecentrifugation, to yield a "brown juice."

To obtain the ribulose 1,5-diphosphate carboxylase, the brown juice iscooled to and stored at a temperature at which crystallization willoccur, usually at or below room temperature. Particularly good resultshave been obtained by cooling the brown juice to about 8° C. for about24 hours. The crystallized ribulose 1,5-diphosphate is separated fromthe supernatant liquid by filtration or centrifugation.

The supernatant liquid contains Fraction II proteins and a portion ofuncrystallized Fraction I protein. These proteins may be recovered byacidifying the supernatant liquid which causes their precipitation. Bestresults are obtained by acidification to a pH of about 4.5. Less proteinis precipitated if a pH of 4.0 or pH 5.0 is employed.

The foregoing description has stressed the process in which the entirepulp is heated prior to separation of the liquid portion. However, aspreviously indicated, the heating step can be carried out after theliquid portion containing a suspension of the green-pigmented materialsis separated from the pulp. Furthermore, where it is not desired toobtain Fraction I protein separately, the heat treatment described abovecan be dispensed with and the liquid portion acidified to precipitatethe water-soluble proteins without separating the Fraction I andFraction II proteins.

After deproteinization, the resulting clear brown fluid, now nearlydevoid of all protein, but containing all of the other water-solublenatural products that were present in the tobacco plants, is treatedwith base to adjust the pH to greater than 7.0 and then steam-distilledto remove nicotine. After steam distiallation, the fluid is evaporatedto dryness to obtain a brown residue having a consistency about likethat of molasses. This residue is retained for further use, as describedhereinafter.

The pulp is squeezed to separate the liquid portion, which is treated asdescribed above. The residue remaining, a coarse green materialcontaining about 70 percent water, is suspended in a suitable solvent toextract the green-pigmented material. Methanol or acetone can be usedfor this purpose. In the case of methanol, a sufficient volume of 100percent methanol is added so that the methanol will be diluted by thewater remaining in the green residue to a concentration of about 90percent methanol. When acetone is used, it is used in an amount which isdiluted to a concentration of 80 percent acetone by the residual waterin the green residue. When the green residue is suspended in theselected solvent, extraction of the green color is rapid and complete,leaving a light tan to nearly white, fluffy fibrous material from whichthe solution of pigmented material is easily separated by squeezing,filtration or other suitable process.

The residual solvent is removed from the fibrous residue by evaporationand produces a dry, pleasantly scented, decolorized residue which issubsequently further treated as described below.

The green sludge obtained by separation from the liquid portion isdecolorized in essentially the same manner as the coarse residuematerial described above. Thus, the green sludge is suspended in eithermethanol or acetone, or other suitable solvent, to extract the pigmentedmaterials to leave a nearly white, dry product which consists of thewater-insoluble proteins and starch in the tobacco leaves.

The pigmented materials obtained from the coarse solids and the greensludge are recovered by separating the decolorized solids from theextracted liquid from which the methanol or acetone is evaporated. Thisresults in a suspension comprising globules of water-insolublegreen-pigmented materials suspended in water which containswater-soluble yellow pigmented materials. The latter are recovered byevaporation of the water for subsequent utilization.

Separation of the green-pigmented materials from the coarse greenresidue or the green sludge can be accomplished separately or bycombining the solvent extracts from the decolorization of the twosolids.

It is known that the yellow, water-soluble pigmented material isolatedin this way from the green pigmented material oxidizes during the curingprocess carried out on conventional tobacco to obtain materials having aquinoid-type structure. Therefore, in a preferred embodiment of thepresent invention, this material, or at least a portion thereof, isoxidized to obtain similar products. Preferably, the oxidation iscarried out by adding sufficient ammonium hydroxide or other volatilebases which have boiling points similar to or below that of water or bybubbling ammonia gas through the aqueous solution containing the yellowpigmented material to adjust the pH to a value of about 10.5. Air oroxygen is then bubbled through the solution until it turns brown. Thebrown solution is then heated to drive off ammonia and volatile basesincluding nicotine. The resulting brown solution is retained for furtheruse in the manner described hereinafter.

The green-pigmented materials obtained by evaporation of the methanol oracetone solvent from the solution of pigment materials are, in apreferred embodiment of the present invention, further treated toseparate green-pigmented materials from orange-yellow pigmentedmaterials which are also water-insoluble. To do this, the tar-likematerial obtained when the solvent is evaporated from the solution ofpigmented materials is suspended in 2 N potassium hydroxide containing20 percent methanol and then heated in a closed vessel or otherrefluxing device at about 60° C. until the material has dissolved.

When all the material has been dissolved, the solution is cooled to 25°C. and the dissolved material subjected to a liquid-liquid extractionusing a non-polar solvent to extract the orange-yellow pigmentedmaterials from the solution. Suitable solvents include non-polaraliphatic solvents such as petroleum ether, pentane, hexane or heptane;chlorinated solvents such as chloroform or dichloromethane; aromaticsolvents such as benzene or toluene, and cycloaliphatic solvents such ascyclopentane or cyclohexane.

The non-polar solvent extracts the orange-yellow pigmented materialsfrom the solution and these materials are recovered by evaporation ofthe non-polar solvent employed. The green pigments are not extracted bythe non-polar solvents but remain dissolved in the potassiumhydroxide-methanol solution. The orange-yellow pigmented materials areretained for further use as described hereinafter.

As a result of the several steps described above, the tobacco has beenseparated into components which are substantially free of protein,nicotine and green-pigmented materials. These materials can berecombined to obtain a deproteinized tobacco freed of nicotine and greenpigment which can be utilized in cigarettes or other smoking products.This is accomplished by placing the decolorized coarse solid material ina rotating container which is equipped with sprayers and heating devicessufficient to maintain the container at a temperature of from about 70°C. to about 80° C. The container is also provided with means forcirculating air throughout.

The orange-yellow water-insoluble pigment materials and thewater-soluble yellow pigment materials which have not been oxidized aredissolved in a suitable solvent, for example, ethyl alcohol, and aresprayed over the decolorized residue at a controlled rate of sprayingwhich permits the residue to absorb these materials and to begin toassume the brownish color characteristic of conventional cured tobacco.

Next, the brown solution of water-soluble material obtained from theoxidation of a portion of the yellow-pigmented material is sprayed overthe solid material, again at a controlled rate of spraying such that thesolid material can absorb the solution, to add additional colorenhancement and to restore additional flavorants and odoriferouscomponents.

Finally, the molasses-like brown residue obtained from the liquidportion by removal of the water-soluble proteins is redissolved in waterand applied to the residue to add yet additional color, aroma and flavorto the reconstituted tobacco product. The agitation of the reconstitutedtobacco product is continued until the moisture content reaches a levelof about 15% to about 20%. The product obtained in this way closelyresembles in hue and texture the reconstituted tobacco product obtainedfrom conventionally cured tobacco and used as a filler in, for example,cigarette manufacture.

As shown by the table below, the tobacco product obtained from bothburley and flue-cured type tobaccos, using the process of the presentinvention, has a reduced content of nicotine, reducing sugar, andproducts of petroleum ether extraction, i.e., tar content. T,0170

Furthermore, as those skilled in the art will appreciate, by regulatingthe proportions of the materials sprayed over the decolorized residueobtained as a product of the process of this invention, differingcharacteristics can be given the reconstituted tobacco product. Forexample, the product can be modified to have a low content ofterpenoids, sterols, carotenoids and other hydrocarbons. Reconstitutedtobacco with a low content of fatty acids and lipids or reconstitutedtobacco with a low content of polyphenols and organic acids is possible.It is also possible to reconstitute tobacco in a way that it containseither low amounts or enriched amounts of reducing sugars.

Yet another advantage of the process of the present invention is thatthe tobacco can be cultivated in a way that is less labor-intensive thanconventional cultivation. For example, the tabacco plants need not begrown to maturity and harvested in the conventional way. Instead, theplants can be grown and harvested mechanically before maturity and thenprocessed in accordance with the present invention to obtain a productwhich is suitable for use as a filler in cigarettes and other tobaccoproducts, with a corresponding reduction in the time and labor requiredto cultivate tobacco in the conventional way.

Finally, if the process of the present invention involvesdeproteinization of the tobacco in the manner described by S. G. Wildmanand P. Kwanyuen in their copending application, a commercially valuablewater-soluble protein can be isolated from the tobacco leaves and, atthe same time, a tobacco product obtained which is lower in protein,nicotine and tars.

The present invention has been described in terms of the embodimentswhich are presently preferred. However, in view of the foregoingdescription of the invention, those skilled in the art will recognizethat the process of the invention may be modified without departing fromthe scope and spirit of the invention.

Accordingly, the invention is to be limited only by the appended claims.

We claim:
 1. A process for treating tobacco leaves to obtain a tobaccoproduct suitable for use in a smoking product from which proteins,nicotine and tar have been removed comprising the steps:(a) convertingthe leaves to a pulp comprising a mixture of a coarse solid materialportion and a liquid portion, the liquid portion containingwater-soluble plant material and a suspension of finely particulatematerial; (b) separating the coarse solid material from the liquidportion; (c) separating the finely particulate material from the liquidportion; (d) separating water-soluble protein and nicotine from saidliquid portion; (e) separating pigmented material from said coarse solidmaterial and said finely particulate material; (f) separating greenpigmented components of said pigmented material from non-green pigmentedcomponents; and (g) recombining the depigmented coarse solid material,the liquid portion from which protein and nicotine have been removed andthe non-green pigmented components.
 2. A process according to claim 1wherein the liquid portion is heated to a temperature below that atwhich protein in said liquid portion denatures for a time sufficient toinduce ribulose 1,5-diphosphate carboxylase contained in said liquidportion to crystallize when the liquid portion is cooled followed bycooling the liquid portion to crystallize the ribulose 1,5-diphosphatecarboxylase.
 3. A process according to claim 2 wherein crystallizedribulose 1,5-diphosphate carboxylase is separated from the liquidportion and acid added to the liquid portion to precipitate residualwater-soluble protein.
 4. A process according to claims 2 or 3 whereinthe liquid portion is heated prior to separation from the coarse solidmaterial.
 5. A process according to claim 4 wherein the heating is fromabout 48°-52° C.
 6. A process according to claims 1, 2 or 3 wherein thenicotine is removed from the liquid portion by steam distillation.
 7. Aprocess according to claims 1, 2 or 3 wherein the pigmented material isseparated from the coarse solid material and the fine particulatematerial by solvent extraction.
 8. A process according to claim 7wherein the solvent is selected from methanol or acetone.
 9. A processaccording to claim 7 wherein the pigmented material is separated into awater-soluble fraction comprising yellow-pigmented material and awater-insoluble fraction comprising water-insoluble green pigmentedmaterial and orange-yellow pigmented material.
 10. A process accordingto claim 9 wherein at least a portion of said water-soluble yellowpigmented material is oxidized as an aqueous solution.
 11. A processaccording to claim 10 wherein the solution is adjusted to a pH of about10.5 by the addition of ammonium hydroxide and a source of oxygenselected from air or oxygen is bubbled through the solution until itturns brown and the brown solution heated to remove volatile bases andnicotine.
 12. A process according to claim 9 wherein the water-insolublefraction is separated into green-pigmented material and orange-yellowpigmented material.
 13. A process according to claim 12 wherein toseparate the orange-yellow pigmented material from the green-pigmentedmaterial, the water-insoluble fraction is dissolved in 2 N potassiumhydroxide containing methanol and the resulting solution extracted witha non-polar solvent to remove orange-yellow pigmented material.
 14. Aprocess according to claim 13 wherein the non-palor solvent is selectedfrom aliphatic solvents, chlorinated solvents, aromatic solvents andcyclo-aliphatic solvents.
 15. A process according to claim 1 wherein theliquid portion is heated to facilitate separation of the finelyparticulate material.
 16. A process according to claim 15 wherein theliquid portion is heated from about 48°-52° C.
 17. A process accordingto claims 15 or 16 wherein the heating is accomplished prior toseparation of the coarse solid material from the liquid portion.
 18. Aprocess according to claims 15 or 16 wherein the separation ofwater-soluble protein from the liquid portion is accomplished by addingacid to the liquid portion to precipitate the water-soluble protein. 19.A process according to claim 18 wherein the nicotine is removed from theliquid portion by steam distillation.
 20. A process according to claims15 or 16 wherein the nicotine is removed from the liquid portion bysteam distillation.
 21. A process according to claims 15, 16 or 19wherein the pigmented material is separated from the coarse solidmaterial and the fine particulate material by solvent extraction.
 22. Aprocess according to claim 21 wherein the solvent is selected frommethanol or acetone.
 23. A process according to claim 21 wherein thepigmented material is separated into a water-soluble fraction comprisingyellow-pigmented material and a water-insoluble fraction comprisingwater-insoluble green pigmented material and orange-yellow pigmentedmaterial.
 24. A process according to claim 23 wherein at least a portionof said water-soluble yellow pigmented material is oxidized as anaqueous solution.
 25. A process according to claim 24 wherein thesolution is adjusted to a pH of about 10.5 by the addition of ammoniumhydroxide and a source of oxygen selected from air or oxygen is bubbledthrough the solution until it turns brown and the brown solution heatedto remove volatile bases and nicotine.
 26. A process according to claim23 wherein the water-insoluble fraction is separated intogreen-pigmented material and orange-yellow pigmented material.
 27. Aprocess according to claim 26 wherein to separate the orange-yellowpigmented material from the green-pigmented material, thewater-insoluble fraction is dissolved in 2 N potassium hydroxidecontaining methanol and the resulting solution extracted with anon-polar solvent to remove orange-yellow pigmented material.
 28. Aprocess according to claim 27 wherein the non-polar solvent is selectedfrom aliphatic solvents, chlorinated solvents, aromatic solvents andcyclo-aliphatic solvents.
 29. A process for treating tobacco leaves toobtain a tobacco product suitable for use in a smoking product fromwhich proteins, nicotine and tar have been removed comprising thesteps:(a) converting the leaves to a pulp comprising a mixture of acoarse solid material portion and a liquid portion, the liquid portioncontaining water-soluble plant material and a suspension of finelyparticulate material; (b) heating the liquid portion to a temperaturebelow that which denatures protein dissolved in the liquid portion; (c)separating the coarse solid material from the liquid portion; (d)separating the finely particulate material from the liquid portion; (e)adding acid to the liquid portion to precipitate the dissolved proteincontained therein; (f) steam distilling the liquid portion to removenicotine therefrom; (g) separating pigmented material from the coarsesolid material and the finely particulate material by solventextraction; (h) separating said pigmented material into a water-solublefraction comprising yellow pigmented material and a water-insolublefraction comprisng green pigmented material and orange-yellow pigmentedmaterial; (i) separating the green-pigmented material and orange-yellowpigmented material; and (j) recombining the depigmented coarse solidmaterial, the liquid portion from which protein and nicotine have beenremoved and the non-green pigmented components.
 30. The product of theprocess of claims 1, 2, 15 or 29.